Hi. I suspect heat soak problems with Taiwan made replacement starter.
Hard to crank when warm, or no crank at all before cooling down.
Would a genuine Delco starter tolerate more heat?

I would suspect that a starter not working in these conditions is a bad starter, no matter the country of origin.

You may also wish to check your battery cables and terminals for corrosion, and check the charging system to make sure it is putting out properly too.

If I truly believed heat was the issue, and the starter was to blame, I would stick the starter in the oven to heat for a while before bench testing. The lowest typical oven setting is 150-175, which I think would be perfect. That should tell you everything.

Some of these starters had heat shields....but more likely the starter...

..the second starter with the same problem in 5 months. Luckily there is 6 month warranty on them. I also wrapped it in a heat shield, but it did not solve the problem.